JPS6085687A - Superimposing device - Google Patents

Abstract

PURPOSE:To prevent fluctuation of a screen and generation of a noise even when modes are alternately changed while recording pictures on a VTR by synthesizing and outputting the second complex image signal which is synchronized with an arrival signal, if the whole picture is intended for a computer as long as a video signal is coming in from outside. CONSTITUTION:When the complex image signal is coming into an input terminal 1, the complex image signal is introduced into an input terminal A in a composite circuit 14 through a SW1, and a carrier chrominance component of 3.58MHz, which is synchronized with a color burst signal of the complex image signal, is introduced into a chroma signal forming circuit 12 through a SW2. When a Y signal forming circuit 11 from the computer outputs a color bar signal, the output of a hybrid circuit 13 turns a switch 16 on and a switch 15 off while a mode changeover signal is at an H level, and turns the switch 15 on and the switch 16 off while the mode changeover signal is at an L level. The output of the hybrid circuit 13 utilizes the video signal as it is, which is inputted from outside for the synchronizing signal and the color burst signal, and is composed into a signal which is combined with the color bar signal from the computer.

Description

[Detailed Description of the Invention] [Technical Field] The present invention relates to a television superimposing device, and more specifically, it inputs an external video signal such as a television broadcast or a video recorder output, and superimposes a graphic image created internally. The present invention relates to a device that mixes a video signal such as one character with the video signal and outputs a synthesized video signal.

BACKGROUND TECHNOLOGY Recently, a device has been put into practical use that combines images from television broadcasts, video recorder output, etc. with two computer-generated figures, etc., and displays them. ,B.

A method in which signals are synthesized at the input stage of the cathode ray tube,
The signal synthesized by this device was not an NTSC video signal, and therefore could not be recorded on a video recorder.

In response, the present inventors equipped a personal computer with a function to create a video signal of nine graphic characters, etc., and replaced this video signal with a portion of an externally inputted NTSC video signal to create a composite video signal. We have separately proposed a new superimposing device that outputs an NTSC video signal containing this composite video signal. The present invention has been made in connection with that novel invention.

<Object of the Invention> The object of the present invention is to propose a countermeasure when there is no video signal input from the outside, and to provide a superimposed image that does not cause image shaking or noise when switching between the presence and absence of an externally arriving signal. The purpose of the present invention is to provide a pose device.

<Configuration of the Invention> The superimposing device of the present invention generates an internal video signal obtained by superimposing a chroma signal on a first composite video signal input from the outside and a character/figure signal internally formed by a computer or the like. a detection device for detecting the presence or absence of the first composite video signal;
A synchronizing means for generating the internal video signal in synchronization with the first composite video signal, an internal synchronizing signal generating means for generating a synchronizing signal related to the internally formed character and graphic signal, and actuated by the detecting device. A switching circuit is provided to
The present invention is characterized in that, depending on the presence or absence of the detection signal, either the first composite video signal or the internal synchronization signal is introduced into the synthesis circuit through the switching circuit.

<Example> The drawing is a circuit block diagram of an embodiment of the present invention.

A first composite video signal such as a television broadcast or a video recorder output is input to the input terminal 1. The synchronization separation circuit 2 extracts from the first composite video signal a horizontal synchronization signal 11sync, a one-shot pulse signal BP for color burst extraction, a horizontal drive pulse HD and a vertical drive pulse VD.
Output. The burst signal extraction circuit 3 extracts the color burst signal of the video signal arriving from the outside, and uses the APC lock circuit 4 which phase-locks the output of the crystal oscillator to extract a continuous 3.58 MHz color burst signal that is color-synchronized with the chroma signal of the incoming video signal. Obtaining a carrier color signal. The no-signal detection circuit 5 detects the presence or absence of the first composite video signal based on the output signal 11sync of the synchronization separation circuit 2 and VD.

The clock signal of the oscillator 6 is frequency-divided by the frequency dividing circuit 7 to obtain an internal frequency of 3.58 MHz. Synchronous controller 8
The signals HD and VD introduced from the synchronization separation circuit 2 and the clock of the oscillator 6 are input to the circuit, and the clocks are frequency-divided to output internal synchronization signals Hsync and Vsync as well as the signals HD and VD or the signal Hsync.

Vsync is introduced into the character/figure generator 9 to suppress the output of R, G, and B signals during the synchronization signal period.

Furthermore, the synchronous controller 8 outputs a mode switching signal based on a mode switching instruction given to the keyboard 10. Modes that can be selected here include: 1) a video mode in which only an externally arriving video signal is output; 2) a superimpose mode in which a superimposed signal is output; and 2) a computer mode in which only a computer screen is output.

Y signal forming circuit 11 is R, G, B by computer.
From the signals, a Y signal is formed according to the ratio of Y=0.59G+〇, 31R+0.11B. Chroma signal forming circuit 12
is yellow, cyan, and green by appropriately phase shifting the 3.58MHz clock signal.

A computer chroma signal is obtained by creating phases corresponding to the hues of a total of six colors, magenta, red, and blue, and selecting them according to computer R, G, and B signals. Mixing circuit 13 mixes the computer Y signal and the computer chroma signal to form an internal (second) video signal.

However, this video signal does not include a synchronization signal, bar, and gt signals.

The synthesis circuit 14 connects the synchronization signal input line and the luminance signal input line '2.
Either one of the signals on the input lines A and B of the book is led to the output line C. Each of the two input lines A and B has a switch 15.1.
6 are provided, and one of them is controlled to be turned on and the other to be turned off in accordance with the mode switching signal. That is, in the aforementioned video mode (■), only the switch 15 is always on, and in the computer mode (■) and when there is no external incoming signal, only the switch 16 is always on. When there is an incoming signal and in superimpose mode (2), the switch 15 is turned on during the synchronization signal period, and turned on and off during the luminance signal period as appropriate depending on the content of superimposition.

Internal synchronization signal Hsy output from synchronous controller 8
nc and Vsync are converted into a composite synchronization signal by a mixer 17, and are further supplied through a burst gate switch that is turned on only when the synchronization signal Hsync is present.
H2Il! A black burst signal is generated by mixing the color sending signal with the mixer 19. On the other hand, the changeover switch SWI operated by the detection signal of the above-mentioned no-signal detection circuit 5
and SW2. The switch SWI selects the input signal to the input line A of the synthesis circuit 14, and when no signal is detected (
In the illustrated state), the black burst signal which is the output of the mixer 19 is introduced, and when there is a signal, the arrival signal of the external input terminal 1, the first composite video signal, is introduced. switch SW2
is the 3,58MH input to the chroma signal forming circuit 12
It selects the z clock signal, and when no signal is detected (the state shown in the figure), the output of the frequency divider circuit 7 is introduced, and when a signal is detected, the output of the APC lock circuit 4 is introduced.

Next, the effect will be explained.

When a composite video signal arrives at the input terminal 1, the composite video signal is directly introduced to the input line A of the combining circuit 14 through the SWI, while the 3rd composite video signal synchronized with the color burst signal of the first composite video signal , 58 MHz lll color sending signals are introduced into the chroma signal forming circuit 12 through SW2. To explain the case where the computer-based Y signal forming circuit 11 outputs, for example, a color par signal as shown in FIG. teeth,
The waveform will be as shown in Figure 2 (B1). If the mode switching signal is the waveform shown in Figure 2 (C1), this will be the H level period, the switch 16 is on, the switch 15 is off, and the L level period. , switch 15 is on, switch 16 is on
is turned off. As a result, the output waveform of the synthesis circuit 14 is as shown in FIG.
This is combined with a computer-generated color bar signal.

Here, when the external input video signal disappears, the no-signal detection circuit 5 detects this, and accordingly, SWI and SW2
is switched. At this time, the synchronization signals 11syne and Vsyne output from the synchronization controller 8 are generated by dividing the clock signal of the oscillator 6, and are synchronized with the 3.58MHz carrier color signal output from the frequency division circuit 7. A black burst signal with no color circumference is introduced to the input line A of the synthesis circuit 14 through the SWI, and
The 3.58 MHz Jll color feeding signal is introduced into the chroma signal forming circuit 12 through SW2, and is synthesized by the synthesizing circuit 14 in the same manner as in the above case.

<Effects of the Invention> According to the present invention, as long as a video signal arrives from the outside, even if the entire screen is generated by a computer, a second composite video signal synchronized with the incoming signal can be synthesized and output. Therefore, even when the mode is alternately switched while recording on a VTR device, screen shaking and noise will not occur.

Also, even when the external incoming signal becomes nothing (as common knowledge),
Since it immediately switches to internal synchronization, there is no problem in creating video signals in computer mode (in addition, the internal 3.58M
Hz clock and internal 11syne.

Since a frequency division relationship is established between Vsyne and Vsyne, there is no phenomenon of rotating colors on the screen, and a high quality video signal can be obtained.

[Brief explanation of drawings]

FIG. 1 is a circuit block diagram showing an embodiment of the present invention, and FIG. 2 is an explanatory diagram of the operation of the embodiment. Patent Applicant Sharp Corporation Agent Patent Attorney Arata Nishida Figure 2

Claims (1)

[Claims] (11) A first composite video signal input from the outside and an internal video signal obtained by superimposing a chroma signal on a character/figure signal internally formed by a computer, etc. are synthesized by a synthesis circuit. a detection device for detecting the presence or absence of the first composite video signal;
A synchronizing means for generating the internal video signal in synchronization with the first composite video signal, an internal synchronizing signal generating means for generating a synchronizing signal related to the internally formed character and graphic signal, and actuated by the detecting device. A switching circuit is provided to
A superimposing device characterized in that either the first composite video signal or the internal synchronization signal is introduced into the synthesis circuit through the switching circuit depending on the presence or absence of the detection signal. (2) Either the first carrier color signal synchronized with the burst signal of the composite video signal or the internally generated second carrier color signal is activated by the detection device. 2. The superimposing device according to claim 1, wherein the superimposing device is introduced into the internal video signal generator through a switching circuit.